[ 297 J : 
XLIV. An Abstract of a Memoir on Physical Geology ; with 
a further Exposition of certain Points connected with the 
Sulject. By W. Horxins, Esq., M.A., F.G.S., of St. Peter’s 
College, Cambridge.* 
JN a memoir entitled “ Researches in Physical Geology,” 
lately printed for the Transactions of the Cambridge Phi- 
losophical Society, I have endeavoured to develop, by reason- 
ing founded on mechanical principles, and by mathematical 
methods, the effects of an elevatory force acting simulta- 
neously at every point beneath extensive portions of the crust 
of the earth, in producing in it dislocations and elevations 
such as we now recognise. I have not there, however, at- 
tempted to give any exposition of the mechanical principles 
on which the investigations are founded, beyond what was 
necessary to make the subject intelligible to persons familiar 
with investigations of a similar character ; but, with the hope 
that the interest which the subject of elevations must always 
possess in the estimation of the speculative geologist may 
appertain in some measure to any new theoretical views re- 
specting it, I have now been induced to attempt a somewhat 
more detailed and popular exposition of the mechanical con- 
siderations which have entered into my own investigations, 
and which must in some measure, I conceive, enter into all 
others on similar points possessing any claim to a demonstra- 
tive character. I cannot expect to remove difficulties inhe- 
rent in such investigations, and which must be felt to be con- 
siderable even by those best prepared to enter upon them; 
but if I should succeed in so far diminishing them as to ren- 
der the subject more accessible by the only way in which, in 
my Opinion, it can be successfully approached, my object will 
be accomplished. What I have now written may be consi- 
dered as an abstract of a considerable portion of my memoir, 
with a somewhat more detailed exposition of several points 
connected with the subject of it. 
When natural phenomena, characterized by general laws, 
have suggested to us a general cause to which they may be re- 
ferred, our first object must be to investigate the consequences 
of this cause acting under certain conditions, and to compare 
our results with those deduced from observation. Observa-~ 
tion, however, unaided by theory, can rarely accomplish 
more than to detect approximations, more or less accurate, 
to those perfectly definite laws which the phenomena would 
* Communicated by the Author. 
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